Question

What is the structure of the cartilage?

Answer 1

Cartilage is an avascular, flexible connective tissue located throughout the body that provides support and cushioning for adjacent tissues.Cartilage is a flexible connective tissue that differs from bone in several ways. For one, the primary cell types are chondrocytes as opposed to osteocytes. Chondrocytes are first chondroblast cells that produce the collagen extracellular matrix and then get caught in the matrix. They lie in spaces called lacunae with up to eight chondrocytes located in each.

The base substance of cartilage is chondroitin sulfate, and the microarchitecture is substantially less organized than in bone. The cartilage fibrous sheath is called the perichondrium. The division of cells within cartilage occurs very slowly, and thus growth in cartilage is usually not based on an increase in size or mass of the cartilage itself.

STRUCTURE OF CARTILAGE

chontroblasts:cells that produce cartilage matrix

chondrocytes:mature cartilage that resides in lacunae

Extracellular matrix:protein like substance that embedded in a gell like ground substance

perichondrium:dense irregular connective tissue

TYPES OF CARTILAGE

There are three major types of cartilage: hyaline cartilage, fibrocartilage, and elastic cartilage.

Hayaline cartilage

Hyaline cartilage is the most widespread cartilage type and, in adults, it forms the articular surfaces of long bones, the rib tips, the rings of the trachea, and parts of the skull. This type of cartilage is predominately collagen (yet with few collagen fibers), and its name refers to its glassy appearance.

In the embryo, bones form first as hyaline cartilage before ossifying as development progresses. Hyaline cartilage is covered externally by a fibrous membrane, called the perichondrium, except at the articular ends of bones; it also occurs under the skin (for instance, ears and nose).

If a thin slice of cartilage is examined under the microscope, it will be found to consist of cells of a rounded or bluntly angular form, lying in groups of two or more in a granular or almost homogeneous matrix. These cells have generally straight outlines where they are in contact with each other, with the rest of their circumference rounded.

They consist of translucent protoplasm in which fine interlacing filaments and minute granules are sometimes present. Embedded in this are one or two round nuclei with the usual intranuclear network.

Hyaline cartilage has very few fibers in its matrix, so the matrix usually looks smooth. It is very uniform in appearance. It is surrounded by a membrane called the perichondrium, which provides nutrients to the cartilage since the cartilage tissue has no blood vessels of its own. Articular cartilage is hyaline cartilage on the articular surfaces of bones. As such, it lies inside the joint cavity of synovial joints, bathed in synovial fluid produced by the synovial membrane that lines the walls of the cavity.

Hyaline cartilage is high in collagen, a protein that is found not only in connective tissue but also in skin and bones, and helps hold the body together. It provides support and flexibility to different parts of the body. It is found in structures like the nose, ears, and areas where the ends of the ribs attach to the sternum, and in parts of the respiratory system like the trachea and larynx, where it helps give these parts their form but also gives them some flexibility.

Fibrocartilage

Fibrous cartilage has lots of collagen fibers (Type I and Type II), and it tends to grade into dense tendon and ligament tissue. White fibrocartilage consists of a mixture of white fibrous tissue and cartilaginous tissue in various proportions.

It owes its flexibility and toughness to the fibrous tissue, and its elasticity to the cartilaginous tissue. It is the only type of cartilage that contains type I collagen in addition to the normal type II.

Fibrocartilage is found in the pubic symphysis, the annulus fibrosus of intervertebral discs, menisci, and the temporal mandibular joint.

Elastic cartilage

Elastic or yellow cartilage contains elastic fiber networks and collagen fibers. The principal protein is elastin.

Elastic cartilage is histologically similar to hyaline cartilage but contains many yellow elastic fibers lying in a solid matrix. These fibers form bundles that appear dark under a microscope. They give elastic cartilage great flexibility so it can withstand repeated bending.

Chondrocytes lie between the fibers. Elastic cartilage is found in the epiglottis (part of the larynx) and the pinnae (the external ear flaps of many mammals, including humans).

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